"suppression of menstruation, especially from a cause other than age or pregnancy," 1804, Modern Latin, from Greek privative prefix a- "not" (see a- (3)) + men "month" (see moon (n.)) + rhein "to flow" (from PIE root *sreu- "to flow"). Related: amenorrheal.

"disease characterized by inflammation of, and discharge from, a mucous membrane; a cold in the head or chest," late 14c., from Medieval Latin catarrus, from Late Latin catarrhus, from Greek katarrhous "a catarrh, a head cold," literally "a flowing down," earlier kata rrhoos, ultimately from kata "down" (see cata-) + rhein "to flow" (from PIE root *sreu- "to flow"). Related: Catarrhal; catarrhous.

"morbid frequent evacuation of the bowels," late 14c., diaria, from Old French diarrie, from Late Latin diarrhoea, from Greek diarrhoia "diarrhea" (coined by Hippocrates), literally "a flowing through," from diarrhein "to flow through," from dia- "through" (see dia-) + rhein "to flow" (from PIE root *sreu- "to flow"). Respelled 16c. from diarria on Latin model.

also gonorrhoea, 1520s, from Late Latin gonorrhoia, from Greek gonos "seed" (see gonad) + rhoe "flow," from rhein "to flow" (from PIE root *sreu- "to flow"). Mucus discharge was mistaken for semen. In early records often Gomoria, etc., from folk etymology association with biblical Gomorrah. Related: Gonorrheal; gonorrhoeal.

plural of hemorrhoid; late 14c., emeroudis, from Old French emorroides (13c.), from Latin hæmorrhoidae, from Greek haimorrhoides (phlebes) "(veins) liable to discharge blood," plural of haimorrhois, from haima "blood" (see -emia) + rhoos "a stream, a flowing," from rhein "to flow" (from PIE root *sreu- "to flow"). Related: Hemmorhoidal.

1680s (Hakluyt, 1560s, has Malestrand), name of a famous tidal whirlpool off the northwest coast of Norway, supposed to suck in and destroy everything that approached it at all times (in fact it is not dangerous except under certain conditions), from Danish malstrøm (1673), from older Dutch Maelstrom (modern maalstroom), literally "grinding-stream," from malen "to grind" (from PIE root *mele- "to crush, grind") + stroom "stream" (from PIE root *sreu- "to flow").

The name was used by Dutch cartographers (for example Mercator, 1595). OED says it is perhaps originally from Færoic mal(u)streymur. Popularized as a synonym for "whirlpool" from c. 1841, the year of Poe's "A Descent into the Maelstrom."

word-forming element meaning "current of a stream," but from late 19c. typically in reference to the flow or adjustment of electric current, from Greek rheos "a flowing, stream, current," which is related to rhein "to flow," rhythmos "rhythm" (from PIE root *sreu- "to flow").

"study of the deformation of the flow of matter," 1929, from French rhéologie; see rheo- "current of a stream" + -logy "study of." Related: Rheologist; rheological.

1843, "instrument for regulating or adjusting the resistance in a circuit," coined by English inventor Charles Wheatstone from Greek rheos "a flowing, stream" (see rheo-) + -stat "regulating device." Related: Rheostatic.

late 14c., reume, "watery fluid or humid matter in the eyes, nose, or mouth" (including tears, saliva, mucous discharge from the nostrils), from Old French reume "a head-cold" (13c., Modern French rhume) and directly from Latin rheuma, reuma, from Greek rheuma "discharge from the body, flux; a stream, current, flood, a flowing," literally "that which flows," from rhein "to flow" (from PIE root *sreu- "to flow").

In old medicine it was conceived as draining from the higher to lower parts of the body and causing ailments if out of balance. Also from late 14c. as "a head-cold, catarrh." The -h- was restored in early Modern English.